For well over sixty years, wheels for automotive passenger vehicles (which includes light trucks as well as passenger cars) adapted for button-hook mounting of pneumatic tires thereon have been fabricated from sheet metal, usually steel, to provide a rolled one-piece rim with a drop-center well to which is affixed a disc (also variously termed "body", "spider", "web" or "center") adapted for mounting the wheel to the hub or other wheel mounting part of the vehicle. Usually the rim is made with both inboard and outboard bead seats and associated tire bead retaining flanges, and the disc is secured to the base of the drop-center well of the rim. Such wheels are well suited for use with tubeless tires and are in extensive use today as so-called "base wheels" or "plain-Jane" wheels utilizing discs of relatively simple, standardized shape. Although more costly highly stylized deep drawn discs have been successfully used since the 1960's to enhance the appearance of such wheels (so-called "styled wheels"), because of the limited opportunity to provide varying appearance and in order to reduce manufacturing cost, removably attached decorative hub caps, wheel covers and/or trim rings have been provided at additional cost as retail customer add-on options to enhance the appearance of "plain Jane" wheels.
Such wheels may also be aesthetically enhanced if used as a "backbone" of composite plastic and sheet metal styled wheels such as those extensively commercialized and sold under the trademark "POLYCAST" by the assignee of applicants herein, Motor Wheel Corporation, Lansing, Mich. Such wheels have a decorative plastic body permanently affixed to the outboard (also variously termed "street-side", "curb-side" or "beauty-side") of the sheet metal "backbone", as set forth in more detail, for example, in Joseph U.S. Pat. No. 5,098,272 and the patents cited therein, and assigned to the assignee herein, Motor Wheel Corporation of Lansing, Mich.
Another effort to enhance the appearance of automotive wheels has been the development of aluminum styled wheels made by such processes as sand casting, permanent die casting, forging, etc., and finished by machining. Such wheels may have the outboard tire bead seat and retaining flange joined integrally with the disc, to impart a so-called "full-face look", and this portion in turn also joined integrally with the remainder of the rim inboard half in a one-piece wheel assembly, or may be made as a two-piece wheel assembly united by welding as exemplified by the Motor Wheel Nobach U.S. Pat. No. 3,506,311. Although such aluminum full-face styled wheels have gained increased popularity in the last decade, they represent a relatively costly solution to the problem of enhancing wheel styling.
A more recent passenger vehicle wheel development, initiated in the 1980's by Motor Wheel Corporation, is the so-called "full-face" sheet metal (e.g. steel) wheel, wherein the disc is a fabricated sheet metal part that extends generally radially outwardly around its outer periphery to also form the outboard tire bead retaining flange to achieve the full-face appearance. A modified dual-bead-seat, single bead-retaining-flange type rim is formed adjacent its outboard edge to provide the outboard bead seat, and the rim free edge is formed to provide a radially in-turned flange which is welded to the inboard face of the full-face disc part. A commercially successful example of such a full-face wheel is that disclosed and claimed in U.S. Pat. No. 4,610,482, to Overbeck et al., also assigned to the assignee herein. Such sheet metal full-face wheels enable the wheel designer to provide a more unique full-face styling appearance to the outboard face of the wheel at lower cost than cast or forged aluminum wheels, while also eliminating the need, associated with plain-Jane wheels, for attaching ornamental wheel covers and their attendant problems and cost.
These full-face sheet metal wheels of the Overbeck et al U.S. Pat. No. 4,610,482 also meet the increased off-set requirement of front wheel drive systems while at the same time providing weight savings over the aforementioned plain-Jane or base wheel type construction. They also satisfy such other demanding parameters as a strong, reliable air-tight circumferential weld joint and a two-piece wheel assembly capable of meeting severe fatigue life specifications required on current O.E.M. automotive vehicle wheels. Many millions of such wheels have been made and sold and are currently in use on automotive passenger vehicles (both passenger cars and light trucks) of both U.S. and foreign manufacture.
As is well understood in the art, the manufacture of such full-face wheels utilizing the one-piece wheel disc/outboard rim flange part, as with high volume wheel disc manufacture in general, requires complex and costly tooling and associated fixtures and transfer equipment and also involves substantial manufacturing processing cost in maintaining such progressive die forming equipment. Many forming stages as well as subsequent manufacturing operations are often required to transform the flat circular sheet metal starting blank into the various configurations, contours and openings involved in providing the central bolt circle wheel mounting portion of the disc, the "window" or "beauty-section" of the disc which extends radially outwardly of the wheel from the center mounting portion, and in the case of full-face wheels, the reversely curved outer edge portion which forms the outboard tire bead retaining flange of the disc.
Also, the design and manufacture of one-piece wheel discs in general require proper material selection and design of the disc blank for cold work stamping and drawing operations. The initial stock thickness must be uniform throughout the blank to permit economical utilization of lower cost sheet metal starting material. The sheet metal starting material chosen, i.e., mild carbon or HSLA steel, aluminum or magnesium, must meet manufacturing formability requirements and strength and flexure characteristics capable of satisfying the severe fatigue load specifications of current automotive passenger vehicle wheels. Since the cyclical stress levels imposed on the wheel during use vary significantly as between the various portions of the wheel disc, both the foregoing disc blank parameters as well as the ultimate cross-sectional configuration and contours of the wheel disc must be selected and designed to accommodate the fatigue life requirements of the most highly stressed areas. This can result in "material overdesign" with respect to the fatigue life requirements of the lower stressed areas of the disc, and the ensuing cost and weight penalties. These considerations also apply to full-face one-piece disc engineering design.
In addition, even for a given style full-face or other type disc wheel design, the need sometimes arises to accommodate variations in bolt circle layout (e.g. number and size) and variations in center hole sizes and configurations. This too can result in high tooling change costs and lead times to make, install and try-out such tooling modifications.
One distinguishing characteristic of such prior full-face aluminum and sheet metal wheel constructions, wherein the one-piece disc provides the outboard tire-bead-retaining flange, is that they have a fixed (non-variable) wheel off-set for any particular full-face wheel part design. By contrast, a "plain-Jane" or "base wheel" construction, because of the telescopic-type press-fit and welded attachment of the peripheral disc flange to the drop-center well of the dual bead rim, permits off-set specifications for a given wheel part to be varied relatively easily without changing the other parameters of the given wheel design, even though reduced brake clearance of such wheel types remains a limitation. Hitherto, if a given full-face wheel design were desired to be retained unchanged, and yet adapted to fit different models of a vehicle having differing wheel off-set requirements, the configuration of the one-piece disc/outboard rim flange part of the wheel had to be re-designed in order to shift the wheel mounting plane relative to the wheel rim. With a sheet metal full-face disc, this in turn entailed a re-tooling of the progressive die cold forming equipment utilized in the transfer press to make this part, thereby incurring the tooling change costs and long lead times involved in the manufacture of such modified tooling as well as in the installation and try-out of the same. This was true even in those instances where the wheel disc/outboard rim flange part was not to be noticably changed in its outboard appearance from the styling standpoint.
Accordingly, it is an object of the present invention to provide an improved full-face wheel construction which permits a wide range of wheel offset variations to be accomplished at reduced cost and without necessarily changing the outboard appearance of the styling area of the full face wheel, and which enables greater optimization of the strength-to-weight ratio of the part, permits heat conductivity to be varied with the parts of the disc construction and allows greater styling variations and by eliminating the need to select a single starting material for the entire wheel disc, while also satisfying the aforementioned wheel manufacturing and wheel product requirements of full-face wheels.
Another object of the present invention is to provide an improved method for making a full-face vehicle wheel construction of the aforementioned character in an economical uniform and reliable manner.